1. Field of the Invention
This invention relates to a driving circuit for a piezo actuator, as an electromechanical transducer, which mechanically drives a pin of impact-type dot-matrix printer.
2. Description of the Related Arts
A piezo element has been promisingly drawing attention as a mean to satisfy the need of high speed actuator used in an impact-type dot-matrix printer head.
However, there is a problem in that the characteristics, particularly capacitance, for a piezo element greatly vary according to its temperature rise. Change in its capacitance value causes voltage variation applied thereto. Accordingly, the mechanical expansion of the piezo element, which is substantially proportional to the applied voltage changes, as well. Accordingly, the mechanical stroke of the pin cannot be always uniform, resulting in non-uniform darkness of the printed dots.